The present invention relates to an optical fiber telescope comprising an optical train wherein a plurality of optical fibers are arranged in cascading stages which include a collecting stage for collecting light in a field of view and a terminal stage located downstream of the collecting stage for receiving light from the collecting stage and passing the collected light through to an optical train output.
Conventional telescope tracking systems are characterized by a number of shortcomings which the optical fiber telescope and the optical fiber telescope-based tracking system of the present invention overcome. Such shortcomings arise as a result of the prior art telescopes utilized in such systems. According to U.S. Pat. No. 3,329,818, known photo-optical camera systems for searching, locating and tracking distant objects such as orbiting satellites and space vehicles generally have large aperture optical systems combined with special tracking apparatus. The patentee points out that such systems have a relatively small field of view and therefore are characterized by a lower probability of target location. Accordingly, U.S. Pat. No. 3,329,818 discloses a photoelectric tracking system including a facet-element, compound optical system comprising a plurality of telescopes. The patentee states that the facet-element, compound optical system makes it possible to have a comparatively wide field of view associated with a long focal length with reduced distortion and aberration. In a preferred embodiment, U.S. Pat. No. 3,329,818 discloses an arrangement of conventional refractor telescopes that provide optical images to associated image orthicon tubes which in turn apply video signals to a camera control system, an array of oscilloscope tubes, and a camera means.
Other prior art optical telescope-based tracking systems utilizing conventional telescopes have been directed to improved apparatus for receiving optical information from the telescope, improved apparatus for converting the received optical information into useful form, and improved apparatus for recording the converted information. For instance, U.S. Pat. No. 4,397,559 discloses a system which converts information carried by electromagnetic radiation into a permanent record. The patentee states that the telescope may be any suitable type and that a refractor telescope was used in reducing to practice an embodiment of the invention.
U.S. Pat. Nos. 3,329,818 and 4,397,559 are representative of prior art systems that rely upon conventional telescopes which require precision optical elements and mounting means for maintaining the optical elements in precise alignment. The former patent discloses a telescope array to increase the field of view and thereby increase the probability of locating the object to be tracked. However, such an array is relatively expensive and very heavy due to the large, high quality mirrors and lenses required for the several telescopes. Also, conventional telescopes are adversely affected by mechanical vibrations, high "g" forces and aerodynamic pressures. Further, conventional telescopes are generally very difficult to design to be resistent to nuclear radiation, commonly known as "hardening" against nuclear radiation. Conventional telescopes also are susceptible to catastrophic failure as a result of damage to the precision optical elements.
There have been improvements in optical systems by providing optical fibers in the optical train of the system. For instance, U.S. Pat. No. 4,641,931 shows a dual magnification telescope including a conventional objective, an optical fiber array, an intensifier tube having an optical fiber input and an eyepiece. The optical fiber array divides the field of view into two portions by means of a bundle of straight fibers and a bundle of tapered fibers which provide a magnification which is less than unity. By so reducing the magnification, the field of view can be increased for viewing relatively close objects.
U.S. Pat. Nos. 2,992,587; 3,187,627; and 3,801,181 show various optical fiber image transfer means having magnifying or demagnifying properties. U.S. Pat. No. 2,992,587 is related to a tapered optical fiber image transfer device wherein the object to be viewed is placed in close proximity to the end of the fiber bundle. U.S. Pat. No. 3,187,627 provides a magnifying tapered fiber bundle as a lens element in a microscope to reduce distortion and improve resolution. U.S. Pat. No. 3,801,181 discloses object lens elements with particular geometries and properties for use in various optical instruments such as fiberscopes, compound lens elements, and optical transmission devices.
Still further, U.S. Pat. No. 4,650,279 relates to a fiber optic lens adapted to connect two physically remote telescopes. Yet other U.S. patents relating to optical elements and optical systems incorporating optical fibers are U.S. Pat. Nos. 4,205,901; 4,671,605; 4,678,332; 4,698,084; and 4,721,859.